1. Field of the Invention
This invention relates to an alloy magnetic recording head.
2. Description of Prior Art
Recently, the magnetic recording technique is now in progress toward high densification. It is necessary for achievement of high density recording to restrict the spread of the magnetic field as much as possible from the viewpoint of record demagnetization. For this purpose, there has been desired a better head construction which ensures contact between the recording medium and the magnetic head, means to measure fine machining of the gap, and the discovery of high saturation magnetic flux density core materials which make it difficult to create magnetic saturation near the core gap (because the use of high coercive force magnetic recording medium is required from the self-demagnetization).
Now, a magnetic head has been recognized to be optimum when it has a narrow gap of high accuracy and uses an iron (Fe), aluminum (Al) and silicon (Si) series magnetic alloy (for example, Sendust) as a core material for the magnetic head of such high performance. Thus, such magnetic head has been earnestly desired in the field of magnetic recording.
However, it has been extremely difficult at this alloy to form at this alloy magnetic heads having narrow gaps of high accuracy from such Fe-Al-Si series alloy which has hindered the use of such magnetic heads. An example of the conventional method for forming an Fe-Al-Si series magnetic alloy (for example, Sendust) is shown in FIG. 1, in which a quartz (SiO.sub.2) film 3 is formed by the spattering at the gap formation surface (the tape transportation surface) of a core 1, of an Fe-Al-Si series magnetic alloy at one side in FIG. 1 and then a core 2 of Fe-Al-Si series magnetic alloy at the other side is stuck to the core 1 by use of silver alloy brazing material 4, for example, a silver-copper-cadmium-zinc series alloy, of a low melting point. In this method, however, the Fe-Al-Si series magnetic alloy and quartz (SiO.sub.2) used at the front gap forming portion at the tape transportation surface are largely different from each other in the coefficient of thermal expansion (the coefficient of thermal expansion of quartz is 1.7.times.10.sup.-6 /.degree.C. and that of Fe-Al-Si alloy, 13.5.times.10.sup.-6 /.degree.C.), so that the quartz film 3 is peeled off from the Fe-Al-Si series magnetic alloy during the tape transportation. This causes deterioration of the gap accuracy, in other words, it causes a break in the gap forming surface. The silver alloy brazing material 4 for a rear gap at the reverse side to the tape transportation surface generally uses a silver-copper-cadmium-zinc series alloy foil of a low melting point in order to increase a bonding strength with the Fe-Al-Si series magnetic alloy. The brazing material is larger in its coefficient of thermal expansion (about 17 to 18.times.10.sup.-6 /.degree.C.) and also larger in its counter diffusion to that of the Fe-Al-Si series magnetic alloy when both the cores 1 and 2 are bonded. This creates a problem in that cracks are developed at the Fe-Al-Si series alloy portion when the melting silver-alloy brazing material is solidified so that, under the influence of such cracks, it becomes difficult to control for the gap width and to ensure that the gap surfaces are parallel with one another.